A focused laser differential interferometer (FLDI) is experimentally characterized via static and dynamic benchtop testing. The static response is probed using a steady, laminar helium jet, and the dynamic response is investigated using an ultrasonic acoustic beam. In the case of the jet, the refractive index field is independently measured using a Mach-Zehnder interferometer operating simultaneously integrated with FLDI. The experimental data for the static response are compared with numerical simulations of the FLDI based on geometric optics and a ray-tracing algorithm, while the dynamic response is compared with an analytical transfer function derived from the same theory. Close quantitative agreement is found between experiment and theory, validating this approach to modeling FLDI performance. Emphasis is given to quantification of the spatial sensitivity of the system which is a key characteristic of FLDI, especially when applied to hypervelocity ground testing facilities where turbulent flow exists in shear or boundary layers outside the core flow.

中文翻译：

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聚焦激光差分干涉仪的静态和动态表征

聚焦激光差分干涉仪 (FLDI) 通过静态和动态台式测试进行实验表征。使用稳定的层流氦射流探测静态响应，并使用超声波束研究动态响应。在射流的情况下，使用与 FLDI 同时运行的 Mach-Zehnder 干涉仪独立测量折射率场。静态响应的实验数据与基于几何光学和光线追踪算法的 FLDI 数值模拟进行了比较，而动态响应则与源自相同理论的解析传递函数进行了比较。在实验和理论之间发现了密切的定量一致性，验证了这种对 FLDI 性能建模的方法。